1. Field of the Invention
This application relates to the field of computer aided design and more particularly to the field of computer modeling.
2. Description of Related Art
Computer-aided design software can be used to construct and manipulate computer drawings of objects referred to as xe2x80x9cmodelsxe2x80x9d. The user is presented with a display of the model on the computer screen and manipulates the model using keyboard commands, a mouse/cursor combination, and other various input means. Changes to the model are reflected in the screen display of the model as the user makes the changes or, alternatively, in response to the user issuing a specific command to update the screen display of the model. In either case, the screen display of the model serves as the main source of model information to the user and as the user""s reference for inputting and changing features of the model.
Although computer-aided design based on three dimensional models has become increasingly prevalent, engineers and other designers continue to use conventional two-dimensional design drawings in many cases. Two-dimensional design drawings present a number of difficulties, one of which is that they are very difficult to read, even to experts. As two-dimensional renderings of different views of three dimensional objects, the drawings necessarily separate relevant information about a unified object into a plurality of different views. This separation requires the user to understand the multiple views, rather than looking at the object as a whole. In addition, some views, such as section cuts, may not match any view that would actually be seen by a viewer of a real object, so that they require substantial imagination on the part of the user. As the complexity of a modeled object increases and as the number of views increases, it can be very difficult to keep track of the relationship of different views and of the relationship of different components within different views.
Despite these problems, two-dimensional drawings remain a standard modeling technique for a wide range of objects in many fields. Accordingly, a need exists for simplifying computer modeling of two-dimensional drawings.
According to the present invention, processing data objects of a two-dimensional drawing includes marking data objects corresponding to annotation, separating the drawing into a plurality of views, and associating each of the data objects corresponding to annotation with one of the views. Separating the drawing into a plurality of views may include constructing a plurality of intersection and proximity graphs and using the graphs to provide a plurality of connected sets, where each set may correspond to one of the views. The border views may be identified by determining which of the views include less than a predetermined number of elements, contain at least two other views, and are not contained in other views.
Marking data objects corresponding to annotation may include identifying arrows, section lines, detail circles, and text. Identifying arrows may include detecting three lines that form a triangle and three-sided polygons. Isosceles triangles and three-sided polygons corresponding to isosceles triangles may be identified arrows if the a side having a different length than two other sides is shorter than the two other sides. Prior to marking data objects corresponding to annotation, degenerate objects may be removed.